Lookup Texture POP
Summary
The Lookup Texture POP in its simplest form takes two attributes (the Lookup Attribute U and the Lookup Attribute V) with values in the 0-1 range and for each point, uses the attribute value as an index into the pixels of a TOP, pulling the four RGBA values, and placing those values into POP attributes.
If the U index is 0, it pulls values from the first column of the TOP, and if the index is 1 it pulls from the last column of the TOP. If the Lookup Index Units menu is set to Pixel Index, The lookup index can be expressed as pixel number, going from 0 to imagewidth-1.
If the index is out of range, the Extend Left and Right menus determine what to do to the index before doing the lookup, such as holding it at 0 or 1, or cycling the value between 0 and 1.
The Output Attribute Scope parameter determine what to do with each of the RGBA pixel values when they are retrieved - you can re-range the value before putting it in the specified output attribute.
You can lookup into a 3D texture TOP by including an attribute component name in the Lookup Attribute W parameter.
See also Lookup Attribute POP, Lookup Channel POP, Curve POP (Lookup page)
Parameters - Lookup Page
Attribute Class
attrclass - ⊞ - Makes the POP operate on point attributes, vertex attributes or primitive attributes where applicable.
- Point
point-
- Vertex
vertex-
- Primitive
primitive-
Group
group - If there are input groups, specifying a group name in this field will cause this POP to act only upon the group specified.
TOP
top - TOP to use for lookup.
Lookup Index Units
indexunit - ⊞ - Units for lookup index attribute.
- Lookup Index Units
indexunit0-
- Lookup Index Units
indexunit1-
- Lookup Index Units
indexunit2-
Pixel Centered Sampling Location
pixelcentered - ⊞ - Enable input remapping to sample pixels centers.
- Pixel Centered Sampling Location
pixelcentered0- Enable the addition of a half pixel offset when using normalized lookup indices.
- Pixel Centered Sampling Location
pixelcentered1-
- Pixel Centered Sampling Location
pixelcentered2-
Cyclic Index
cyclic - ⊞ - When enabled, the index wraps so the end connects back to the start, letting the full range map evenly across the cycle.
- Cyclic Index
cyclic0-
- Cyclic Index
cyclic1-
- Cyclic Index
cyclic2-
Input Extend Mode
inputextend - ⊞ - What happens when the lookup index attribute is outside of the valid range (0 to 1 for normalized, 0 to numPixels-1 for Pixel Index)
- Input Extend Mode
inputextend0- If sampling with your U, V and W outside the texture 0 to 1 range, how to treat the image: as if it is repeating the image outside its range, mirroring it, holding its edge colors, zero.
- Input Extend Mode
inputextend1-
- Input Extend Mode
inputextend2-
Interpolate
interpolate - When on, the TOP can be interpolated between pixels. When off, the nearest pixel used.
Use Depth Offset
usedepthoffset - Enable using the texture's depth offset for Texture 3D TOPs.
Channel Mask
channelmask - Allows to choose which color channels to sample in the TOP.
From Low
fromlow - ⊞ - Reranges the index attribute value.
- From Low
fromlow0-
- From Low
fromlow1-
- From Low
fromlow2-
- From Low
fromlow3-
From High
fromhigh - ⊞ - Reranges the value resulting from the lookup.
- From High
fromhigh0-
- From High
fromhigh1-
- From High
fromhigh2-
- From High
fromhigh3-
To Low
tolow - ⊞ - Sets low value on the output range.
- To Low
tolow0-
- To Low
tolow1-
- To Low
tolow2-
- To Low
tolow3-
To High
tohigh - ⊞ - Sets high value on the output range.
- To High
tohigh0-
- To High
tohigh1-
- To High
tohigh2-
- To High
tohigh3-
Output Attribute Scope
outputattrscope - ⊞ - Name of attribute to output (can choose components of attribute), can choose from menu.
- P
P-
- N
N-
- Color
Color-
- Color.rgb
Color.rgb-
- Tex
Tex-
- PointScale
PointScale-
- LineWidth
LineWidth-
Override Automatic Attribute
overrideautoattr - Whether to override the kind of attribute automatically created based on the POP input and parameters. Allows to specify manually the type and number of components of the new attribute.
Attribute Type
attrtype - ⊞ - The output attribute's data type, default float.
- float
float-
- double
double-
- int
int-
- uint
uint-
- Color
color-
- Color (double)
dcolor-
- Direction
dir-
- Direction (double)
ddir-
Components
attrnumcomps - ⊞ - The number of components in the new custom attribute.
- 1
1-
- 2
2-
- 3
3-
- 4
4-
Default Value
attrdefaultval - ⊞ - Default values of the output attribute components if they cannot be computed.
- Default Value
attrdefaultval0- Default value(s) of the attribute.
- Default Value
attrdefaultval1- Default value(s) of the attribute.
- Default Value
attrdefaultval2- Default value(s) of the attribute.
- Default Value
attrdefaultval3- Default value(s) of the attribute.
Lookup Index Attribute U
lookupindexattr0 - Attribute to use as the index for the U coordinate of the lookup.
Lookup Index Attribute V
lookupindexattr1 - Attribute to use as the index for the V coordinate of the lookup.
Lookup Index Attribute W
lookupindexattr2 - Attribute to use as the index for the W coordinate of the lookup.
Lookup Index Offset
lookupindexoffset - ⊞ - Offset for the lookup index.
- Lookup Index Offset
lookupindexoffset0-
- Lookup Index Offset
lookupindexoffset1-
- Lookup Index Offset
lookupindexoffset2-
Parameters - Common Page
Bypass
bypass - Pass through the first input to the output unchanged.
Free Extra GPU Memory
freeextragpumem - Free memory that has accumulated when output memory has grown and shrunk.
Delete Input Attributes
delinputattrs - Only output which attributes you specify in this POP - helps isolate attributes into a separate branch.
Operator Inputs
- Input 0: -
Info CHOP Channels
Extra Information for the Lookup Texture POP can be accessed via an Info CHOP.
Common POP Info Channels
Common Operator Info Channels
- total_cooks - Number of times the operator has cooked since the process started.
- cook_time - Duration of the last cook in milliseconds.
- cook_frame - Frame number when this operator was last cooked relative to the component timeline.
- cook_abs_frame - Frame number when this operator was last cooked relative to the absolute time.
- cook_start_time - Time in milliseconds at which the operator started cooking in the frame it was cooked.
- cook_end_time - Time in milliseconds at which the operator finished cooking in the frame it was cooked.
- cooked_this_frame - 1 if operator was cooked this frame.
- warnings - Number of warnings in this operator if any.
- errors - Number of errors in this operator if any.
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